Radiation sensitive resin composition

ABSTRACT

A radiation sensitive resin composition which comprises (A) a polymer which becomes alkali-soluble in the presence of an acid and (B) a radiation sensitive acid generator which generates an acid upon irradiation with a radiation, said polymer (A) comprising two recurring units represented by the general formulas (1) and (2) and a recurring unit which acts to reduce the solubility of the polymer is an alkali developer after the irradiation:                    
     wherein R 1  represents a hydrogen atom or a methyl group and R 2  represents a hydrogen atom or a methyl group. Said composition provides a chemically amplified positive resist which can give a fine pattern with a good pattern shape, and said resist is freed from volume shrinkage, peeling failure and adhesive failure, is excellent in dry etching resistance and effectively reacts with various radiations to give a good pattern shape which is excellent in photolithographic process stability, said pattern shape having no thinned portion at the upper part.

BACKGROUND OF THE INVENTION

This invention relates to a radiation sensitive resin composition. Moreparticularly, it relates to a radiation sensitive resin compositionwhich can be used as a resist particularly suitable for fine processingusing a radiation such as ultraviolet ray, deep ultraviolet ray, X rayor charged particle beam.

In the field of fine processing, a representative of which is theproduction of an integrated circuit device, a lithographic technique isnow being developed which enables fine processing in the order ofsubhalfmicron to be effected with good reproducibility. Representativeresists which have recently been used in the lithographic processinclude positive resists using an alkali-soluble resin such as a novolakresin or the like and a quinonediazide type radiation sensitivecompound. However, the performance of these resists approaches its limitand the use thereof in the fine processing in the order of subhalfmicronis accompanied by a great difficulty.

That is to say, these negative and positive resists have heretofore hadsuch a problem that a sufficient theoretical focal depth cannot beachieved when a fine pattern of 0.35 γm or less is intended to be formedby a lithographic technique using an ultraviolet ray such as g ray(wavelength: 436 nm) or i ray (wavelength: 365 nm) or the like from amercury vapor lamp.

Under such circumstances, research has been energetically conducted on alithographic process using deep ultraviolet rays, X rays or electronbeams which can achieve a broader depth of focus in the formation of afine pattern. However, conventional resists have various problems inrespects of pattern shape, sensitivity, contrast, development and thelike when deep ultraviolet rays, X rays or electron beams are used. Thatis to say, in the case of deep ultraviolet rays, the light absorption ofthe resist is too great, and hence, in the case of a negative resist,the pattern shape tends to become a so-called reverse taper shape inwhich the lower part of the pattern is narrower than the upper part,while even in the case of a positive resist, the pattern shape becomes ataper shape and the sensitivity and contrast and the like are alsolowered. In the case of a higher energy radiation such as X ray andelectron beam, in general, the lowering of sensitivity is greater thanin the case of deep ultraviolet ray, and particularly, in the case of apositive resist, such a phenomenon that the solubility in a developingsolution is lowered upon irradiation with a radiation in some casesthrough the solubility should be originally increased upon irradiation.

On the other hand, as a next generation resist, attention is paid to achemically amplified resist containing a radiation sensitive acidgenerator (namely, a compound generating an acid upon irradiation with aradiation), and this resist has such an advantage that the catalyticaction of the acid generated increases the sensitivity to variousradiations.

As those chemically amplified resists which show relatively good resistperformance, there are known, for example, those containing a resinhaving a tert-butyl ester group or a tert-butoxycarbonyl group (forexample, Japanese Patent Application Kokoku No. 2-27,660), thosecontaining a resin having a silyl group (for example, Japanese PatentApplication Kokai No. 3-44,290), those containing a resin having anacrylic acid component (for example, Japanese Patent Application KokaiNo. 4-39,665) and the like. However, it has ben pointed out that thesechemically amplified resists have the respective inherent problems andvarious difficulties accompany the putting them to practical use. Thatis to say, in the system in which a resin having a tert-butyl estergroup or a tert-butoxycarbonyl group is used, the chemical reactionbased on the catalytic action of the acid generated is accompanied bythe liberation of a gas component such as an isobutene gas or a carbondioxide gas, so that the volume shrinkage is caused upon irradiationwith a radiation, and consequently, the pattern shape tends to bedistorted and hence the formation of a high precision pattern isdifficult. The system in which a resin having a silyl group is used hasa good pattern-formability; however, it has such a disadvantage that ascompared with other systems using a resin free from silyl group, it isinferior in peelability from a substrate. In addition, in the system inwhich a resin comprising an acrylic acid component is used, there issuch a disadvantage that the adhesiveness between the resist and thesilicon substrate is insufficient, and there is such a problem that thedry etching resistance is lower than that of a resist using an aromaticresin.

In order to solve the above-mentioned problems, attention has recentlybeen paid to resins having both acrylic acid ester structure and phenolskeleton (see, for example, Japanese Patent Application Kokai Nos.4-251,259; 5-181,279 and 5-113,667).

Resists using these resins have such advantages that the dry etchingresistance is improved as compared with that of a resin having only anacrylic acid recurring unit. However, since a carboxylic acid is formedin the exposed portion, the solubility-in-alkali-developer rate becomestoo high, and there is such a disadvantage that when a resist pattern isactually formed on a substrate, the upper part of the pattern formedbecomes too thin to form an ideally rectangular pattern.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a radiation sensitive resincomposition freed from the above-mentioned problems.

It is a further object of this invention to provide a radiationsensitive resin composition which is free from volume shrinkage, peelingfailure and adhesive failure, can form a high precision pattern and hashigh dry etching resistance.

It is a still further object of this invention to provide a radiationsensitive resin composition excellent as a resist which can effectivelydecompose upon irradiation with various radiations to form a patternwhich is excellent in photolithographic process stability and has therectangular shape whose upper part is not thinned.

It is another object of this invention to provide a radiation sensitiveresin composition excellent in pattern shape, sensitivity, contrast,developability and the like particularly when it is irradiated with deepultraviolet rays, X rays or electron beams.

Other objects and advantages of this invention will become apparent fromthe following description.

According to this invention, there is provided a radiation sensitiveresin composition which comprises (A) a polymer which becomesalkali-soluble in the presence of an acid and (B) a radiation sensitiveacid generator which generates an acid upon irradiation with aradiation, said polymer (A) comprising two recurring units representedby the general formulas (1) and (2) and a recurring unit which acts toreduce the solubility of the polymer of the irradiated portion in analkali developer after irradiation with a radiation:

wherein R¹ represents a hydrogen atom or a methyl group and R²represents a hydrogen atom or a methyl group.

DETAILED DESCRIPTION OF THE INVENTION Polymer (A)

The polymer (A) is a polymer having a recurring unit represented by thegeneral formula (1) (referred to hereinafter as the recurring unit A), arecurring unit represented by the general formula (2) (referred tohereinafter as the recurring unit B) and a recurring unit which acts toreduce the solubility of the polymer of the irradiated portion in analkali developer after irradiation with a radiation (referred tohereinafter as the recurring unit C):

wherein R¹ represents a hydrogen atom or a methyl group and R²represents a hydrogen atom or a methyl group.

In the general formula (1), R¹ is either hydrogen atom or methyl groupand the polymer (A) can have both the recurring unit of formula (1) inwhich R¹ is a hydrogen atom and the recurring unit of formula (1) inwhich R¹ is a methyl group. The proportion of the number of therecurring units A is preferably 5 to 75%, more preferably 20 to 70%,based on the total number of all the recurring units contained in thepolymer (A). When the proportion of the recurring unit A is less than5%, the adhesiveness to a substrate is inferior and there is apossibility of the resist pattern to peel, and when the proportion ismore than 75%, the difference between the solubility-in-alkali-developerrate of the irradiated portion and that of the unirradiated portionbecomes small and hence the resolution has a tendency to reduce.

In the general formula (2), R² is either a hydrogen atom or a methylgroup and the polymer (A) can have both the recurring unit of formula(2) in which R² is a hydrogen atom and the recurring unit of formula (2)in which R² is a methyl group. The proportion of the number of therecurring units B is preferably 10 to 70%, more preferably 20 to 50%,based on the total number of all the recurring units in the polymer (A).When the proportion of the recurring unit B is less than 10%, thesolubility-in-alkali-developer rate of the irradiated portion becomes solow that no pattern is formed. On the other hand, when the proportion ofthe recurring unit B is more than 70%, the amount of the benzene ring inthe polymer (A) becomes insufficient and hence the dry etchingresistance has a tendency to lower.

The recurring unit C is introduced by copolymerization into the polymer(A) in order to improve the pattern shape and resolution performance,and the proportion of the number of the recurring units C can varydepending upon the proportions of the recurring units A and B; however,it is preferably 0.5 to 50%, more preferably 1 to 30%, based on thetotal number of all the recurring units contained in the polymer (A).When the proportion of the recurring unit C is less than 0.5%, itseffect on reducing the solubility-in-alkali-developer rate of theirradiated portion is lacking, so that the upper part of the resistpattern tends to become thinned, while when the proportion is more than50%, the solubility-in-alkali-developer rate becomes so low that thesensitivity of the resist has a tendency to reduce.

The polymer (A) can be produced by radical polymerization, thermalpolymerization or the like of the respective monomers corresponding tothe recurring unit A, the recurring unit B and the recurring unit C. Themonomer corresponding to the recurring unit A (referred to hereinafteras the monomer a) is vinylphenol or α-isopropenylphenol, the monomercorresponding to the recurring unit B (referred to hereinafter as themonomer b) is tert-butyl acrylate or tert-butyl methacrylate, and themonomer corresponding to the recurring unit C (referred to hereinafteras the monomer c) is a monomer having a low solubility in the alkalideveloper, that is, a monomer free from an acidic substituent such assulfonic acid group, carboxyl group, phenolic hydroxyl group or thelike.

Said monomer c includes organic compounds having a carbon—carbon doublebond copolymerizable with the monomer a and the monomer b and having nosaid acidic substituent, and examples of the organic compounds includevinyl group-containing compounds, (meth)acryloyl group-containingcompounds and the like.

Specific examples of the vinyl group-containing compounds as the monomerc include aromatic alkenyl compounds such as styrene, α-methylstyrene,p-methylstyrene, chlorostyrene and the like; hetero atom-containingaromatic vinyl compounds such as vinylpyridine and the like; vinyl estercompounds such as vinyl acetate and the like; vinyl ketone compound suchas methyl vinyl ketone, ethyl vinyl ketone and the like; vinyl ethercompounds such as methyl vinyl ether, ethyl vinyl ether and the like;hetero atom-containing alicyclic vinyl compounds such asvinylpyrrolidone, vinyl lactam and the like. Specific examples of the(meth)acryloyl group-containing compound which is one of the monomers cinclude methyl (meth) acrylate, ethyl (meth)acrylate,propyl(meth)acrylate, (meth) acrylamide, (meth)acrylonitrile and thelike.

The polystyrene-reduced weight-average molecular weight of the polymer(A) (referred to hereinafter as Mw) is preferably 1,500 to 300,000, morepreferably 3,000 to 100,000 from the viewpoint of retaining thesensitivity, heat resistance, developability and resolving power.

Moreover, the ratio of the polystyrene-reduced weight-average molecularweight Mw of the polymer (A) to the polystyrene-reduced number-averagemolecular weight (referred to hereinafter as Mn) of the polymer (A) [theratio is referred to hereinafter as Mw/Mn] is preferably 1 to 5, morepreferably 1.5 to 3.5 from the viewpoint of retaining the sensitivity,heat resistance, developability and resolving power.

As the polymer (A), there may be used a mixed polymer consisting of atleast two polymer mixtures selected from a mixture of the polymersdifferent in the proportions of the monomer a, the monomer b and themonomer c copolymerized in the above-mentioned range and a mixture ofthe polymers different in Mw and/or Mw/Mn in the above-mentioned ranges.Even when the mixed polymer is used as the polymer (A), it is preferablethat the proportions of the monomer a, the monomer b and the monomer ccopolymerized in the mixed polymer, Mw and/or Mw/Mn fall within theabove-mentioned ranges.

Radiation Sensitive Acid Generator (B)

The radiation sensitive acid generator (B) used in this invention,namely, the compound which generates an acid upon irradiation with aradiation includes, for example, onium salt compounds,halogen-containing compounds, sulfone compounds, sulfonate compounds andquinonediazide compounds. More specifically, the following compounds areincluded:

(I) Onium salt compound

Iodonium salts, sulfonium salts, phosphonium salts, diazonium salts,pyridinium salts and the like are included. Preferable arediphenyliodonium triflate, diphenyliodonium pyrenesulfonate,diphenyliodonium dodecylbenzenesulfonate, triphenylsulfonium triflate,triphenylsulfoniumhexafluoroantimonate, diphenyliodoniumhexafluoroantimonate, triphenylsulfoniumnaphthalenesulfonate,(hydroxyphenyl) benzylmethylsulfonium toluenesulfonate and the like.

Particularly preferable are triphenylsulfonium triflate,diphenyliodoniumhexafluoroantimonate and the like.

(II) Halogen-containing compound

Haloalkyl group-containing heterocyclic compounds, haloalkylgroup-containing hydrocarbon compounds and the like are included.Preferable are (trichloromethyl)-s-triazine derivatives such asphenyl-bis(trichloromethyl)-s-triazine,methoxyphenyl-bis(trichloromethyl)-s-triazine,naphthyl-bis(trichloromethyl)-s-triazine and the like;1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane; and the like.

(III) Sulfone compound

β-ketosulfone, β-sulfonylsulfone and their α-diazo compounds thereof andthe like. Preferable are phenacylphenylsulfone, mesitylphenacylsulfone,bis(phenylsulfonyl)methane, bis(phenylsulfonyl)diazomethane and thelike.

(IV) Sulfonate compound

Alkylsulfonic acid esters, haloalkylsulfonic acid esters, arylsulfonicacid esters, iminosulfonates, imidosulfonates and the like are included.

Preferable imidosulfonate compounds are, for example,N-(trifluoromethylsulfonyloxy)succinimide,N-(trifluoromethylsulfonyloxy)phthalimide,N-(trifluoromethylsulfonyloxy)naphthylimide,N-(trifluoromethylsulfonyloxy)diphenylmaleimide,N-(trifluoromethylsulfonyloxy)-bicyclo-[2,2,1]-hept-5-ene-2,3-dicarboximide,N-(trifluoromethylsulfonyloxy)-7-oxabicyclo-[2,2,1]-hept-5-ene-2,3-dicarboximide,N-(trifluoromethylsulfonyloxy)-bicyclo-[2,2,1]-heptan-5,6-oxy-2,3-dicarboximide,N-(camphanylsulfonyloxy) succinimide,N-(camphanylsulfonyloxy)phthalimide,N-(camphanylsulfonyloxy)naphthylimide,N-(camphanylsulfonyloxy)diphenylmaleimide,N-(camphanylsulfonyloxy)bicyclo-[2,2,1]-hept-5-ene-2,3-dicarboximide,N-(camphanylsulfonyloxy)-7-oxabicyclo-[2,2,1]-hept-5-ene-2,3-dicarboximide,N-(camphanylsulfonyloxy)-bicyclo-[2,2,1]-heptan-5,6-oxy-2,3-dicarboximide,N-(4-methylphenylsulfonyloxy) succinimide,N-(4-methylphenylsulfonyloxy)phthalimide,N-(4-methylphenylsulfonyloxy)naphthylimide,N-(4-methylphenylsulfonyloxy)diphenylmaleimide,N-(4-methylphenylsulfonyloxy)-bicyclo-[2,2,1]-hept-5-ene-2,3-dicarboximide,N-(4-methylphenylsulfonyloxy)-7-oxabicyclo-[2,2,1]-hept-5-ene-2,3-dicarboximide,N-(4-methylphenylsulfonyloxy)-bicyclo-[2,2,1]-heptan-5,6-oxy-2,3-dicarboximide,N-(2-trifluoromethylphenylsulfonyloxy) succinimide,N-(2-trifluoromethylphenylsulfonyloxy) phthalimide,N-(2-trifluoromethylphenylsulfonyloxy) naphthylimide,N-(2-trifluoromethylphenylsulfonyloxy) diphenylmaleimide,N-(2-trifluoromethylphenylsulfonyloxy)bicyclo-[2,2,1]-hept-5-ene-2,3-dicarboximide,N-(2-trifluoromethylphenylsulfonyloxy)-7-oxabicyclo-[2,2,1]-hept-5-ene-2,3-dicarboximide,N-(2-trifluoromethylphenylsulfonyloxy)-bicyclo-[2,2,1]-heptan-5,6-oxy-2,3-dicarboximideand the like.

As other sulfonate compounds than the imidosulfonate compounds,preferable are, for example, benzoin tosylate, pyrogallol tristriflate,pyrogallolmethanesulfonic acid triester,nitrobenzyl-9,10-diethoxyanthracene-2-sulfonate and the like.

In the radiation sensitive resin composition of this invention,particularly preferably sulfonate compounds includepyrogallolmethanesulfonic acid triester,N-(trifluoromethylsulfonyloxy)-bicyclo-[2,2,1]-hept-5-ene-2,3-dicarboximide,N-(camphanylsulfonyloxy) naphthylimide,N-(2-trifluoromethylphenylsulfonyloxy) phthalimide,N-(trifluoromethylsulfonyloxy)-bicyclo-[2,2,1]-hept-5-ene-2,3-dicarboximide,N-(camphanylsulfonyloxy)naphthylimide,N-(2-trifluoromethylphenylsulfonyloxy)phthalimide and the like.

(V) Quinonediazide compound

1,2-Quinonediazidesulfonic acid ester compounds of polyhydroxy compoundsare included. Preferable are compounds having a1,2-quinonediazidesulfonyl group such as1,2-benzoquinonediazide-4-sulfonyl group,1,2-naphthoquinonediazide-4-sulfonyl group,1,2-naphthoquinonediazide-5-sulfonyl group, a1,2-naphthoquinonediazide-6-sulfonyl group or the like. Particularlypreferable are compounds having a 1,2-naphthoquinonediazide-4-sulfonylgroup or a 1,2-naphthoquinonediazide-5-sulfonyl group; and likecompounds.

Specifically, the following compounds are mentioned:

1,2-Quinonediazidesulfonic acid esters of (poly) hydroxyphenyl arylketones such as 2,3,4-trihydroxybenzophenone,2,4,6-trihydroxybenzophenone, 2,3,4,4′-tetrahydroxybenzophenone,2,2′,3,4-tetrahydroxybenzophenone,3′-methoxy-2,3,4,4′-tetrahydroxybenzophenone,2,2′,4,4′-tetrahydroxybenzophenone,2,2′,3,4,4′-pentahydroxybenzophenone,2,2′,3,4,6′-pentahydroxybenzophenone,2,3,3′,4,4′,5′-hexahydroxybenzophenone,2,3′,4,4′,5′,6-hexahydroxybenzophenone and the like;

1,2-quinonediazidesulfonic acid esters of bis-[(poly)hydroxyphenyl]alkanes such as bis(4-hydroxyphenyl) methane,bis(2,4-dihydroxyphenyl)methane, bis(2,3,4-trihydroxyphenyl)methane,2,2-bis(4-hydroxyphenyl) propane, 2,2-bis(2,4-dihydroxyphenyl)propane,2,2-bis-(2, 3,4-trihydroxyphenyl)propane and the like;

1,2-quinonediazidesulfonic acid esters of (poly) hydroxyphenylalkanessuch as 4,4′-dihydroxytriphenylmethane,4,4′,4″-trihydroxytriphenylmethane,2,2′,5,5′-tetramethyl-2″,4,4′-trihydroxytriphenylmethane,3,3′,5,5′-tetramethyl-2″,4,4′-trihydroxytriphenylmethane,4,4′,5,5′-tetramethyl-2,2′,2″-trihydroxytriphenylmethane,2,2′,5,5′-tetramethyl-4,4′,4″-trihydroxytriphenylmethane,1,1,1-tris(4-hydroxyphenyl) ethane,1,1-bis(4-hydroxyphenyl)-1-phenylethane, 1,1-bis(4-hydroxyphenyl)-1-(4′-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl)ethaneand the like;

1,2-quinonediazidesulfonic acid esters of (poly) hydroxyphenylflavanssuch as 2,4,4-trimethyl-2′,4′,7-trihydroxy-2-phenylflavan,2,4,4-trimethyl-2′,4′,5′,6,7-pentahydroxy-2-phenylflavan and the like.

Particularly preferable are 1,2-naphthoquinonediazide-4-sulfonic acidester compounds of1,1-bis(4-hydroxyphenyl)-1-(4′-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl)ethanesrepresented by the following structural formula (3):

wherein D represents a substituent of the formula (4):

or a hydrogen atom.

In the formula (3), the proportion of D being a substituent of theformula (4) is preferably 75 to 95% on average, particularly preferably80 to 90% on average.

These radiation sensitive acid generators (B) may be used alone or inadmixture of two or more.

The amount of the radiation sensitive acid generator (B) used ispreferably 0.05 to 20 parts by weight, more preferably 0.1 to 15 partsby weight, per 100 parts by weight of the polymer (A). When the amountof the radiation sensitive acid generator (B) used is less than 0.05part by weight, it is difficult in some cases to cause chemical reactioneffectively with an acid catalyst generated by irradiation with aradiation. On the other hand, when the amount of the radiation sensitiveacid generator is more than 20 parts by weight, there is a fear thatuneven coating is caused when the composition is applied to a substrateand scum and the like are formed during development.

Into the radiation sensitive resin composition of this invention may beincorporated, if necessary, an alkali-solubility controller, anacid-diffusion controller or the like as explained below.

Alkali-Solubility Controller

The alkali-solubility controller is a compound which has such propertiesthat the alkali-solubility of the radiation sensitive resin compositionis controlled, and when it is decomposed, for example, is hydrolyzed, inthe presence of an acid, the alkali-solubility-controlling effect of thealkali-solubility controller on the radiation sensitive resincomposition is reduced or lost, or the alkali-solubility of theradiation sensitive resin composition is accelerated by the controllerafter decomposition.

As such an alkali-solubility controller, there may be mentioned, forexample, compounds whose acidic functional groups such as phenolichydroxyl group, carboxyl group and the like have been substituted byacid-decomposable groups.

The alkali-solubility controller may be either a low molecular weightcompound or a high molecular weight compound, and preferable controllersare compounds obtained by substituting an acid-decomposable group forthe acidic functional group of polyphenol compounds having two or morephenolic hydroxy groups, such as bisphenol A, bisphenol F, bisphenol Sand the like, and carboxylic acid compounds such as hydroxyphenylaceticacid and the like.

Specifically, compounds represented by the following structural formulas(a) and (b) are included:

Also, as the high molecular eight alkali-solubility controller, theremay be used an acid-decomposable group-containing resin.

The term “acid-decomposable group” used herein means a substituent whichis decomposed in the presence of an acid to make the compound or resin,the acidic functional groups of which have been substituted by the aciddecomposable groups, alkali-soluble.

Such acid-decomposable groups include, for example, substituted methylgroups, 1-substituted ethyl groups, 1-branched alkyl groups, allylgroups, germyl groups, alkoxycarbonyl groups, acyl groups, cyclicacid-decomposable groups and the like.

The above-mentioned substituted methyl groups include, for example,methoxymethyl group, methylthiomethyl group, ethoxymethyl group,ethylthiomethyl group, methoxyethoxymethyl group, benzyloxymethyl group,benzylthiomethyl group, phenacyl group, bromophenacyl group,methoxyphenacyl group, (methylthio)phenacyl group, cyclopropylmethylgroup, benzyl group, diphenylmethyl group, triphenylmethyl group,bromobenzyl group, nitrobenzyl group, methoxybenzyl group,methylthiobenzyl group, ethoxybenzyl group, ethylthiobenzyl group,piperonyl group and the like.

The above-mentioned 1-substituted ethyl groups include, for example,1-methoxyethyl group, 1-methylethyl group, 1,1-dimethoxyethyl group,1-ethoxyethyl group, 1-ethylthioethyl group, 1,1-diethoyxethyl group,1-phenoxyethyl group, 1-phenylthioethyl group, 1,1-diphenoxyethyl group,1-benzyloxyethyl group, 1-benzylthioethyl group, 1-cyclopropylethylgroup, 1-phenylethyl group, 1,1-diphenylethyl group, α-methylphenacylgroup and the like.

The above-mentioned 1-branched alkyl groups include, for example,isopropyl group, sec-butyl group, tert-butyl group, 1,1-dimethylpropylgroup, 1-methylbutyl group, 1,1-dimethylbutyl group and the like.

The above-mentioned silyl groups include, for example, trimethylsilylgroup, ethyldimethylsilyl group, diethylmethylsilyl group, triethylsilylgroup, dimethylisopropylsilyl group, methyldiisopropylsilyl group,tri-isopropylsilyl group, tert-butyldimethylsilyl group,di-tert-butylmethylsilyl group, tri-tert-butylsilyl group,dimethylphenylsilyl group, methyldiphenylsilyl group, triphenylsilylgroup and the like.

The above-mentioned germyl groups include, for example, trimethylgermylgroup, ethyldimethylgermyl group, diethylmethylgermyl group,triethylgermyl group, dimethylisopropylgermyl group,methyldiisopropylgermyl group, triisopropylgermyl group,tert-butyldimethylgermyl group, di-tert-butylmethylgermyl group,tri-tert-butylgermyl group, dimethylphenylgermyl group,methyldiphenylgermyl group, triphenylgermyl group and the like.

The above-mentioned alkoxycarbonyl groups include, for example,methoxycarbonyl group, ethoxycarbonyl group, isopropoxycarbonyl group,tert-butoxycarbonyl group, tert-pentyloxycarbonyl group and the like.

The above-mentioned acyl groups include, for example, acetyl group,propionyl group, butyryl group, heptanoyl group, hexanoyl group, valerylgroup, pivoloyl group, isovaleryl group, lauloyl group, myristoyl group,palmitoyl group, stearoyl group, oxalyl group, malonyl group, succinylgroup, glutaryl group, adipoyl group, piperoyl group, suberoyl group,azelaoyl group, sebacoyl group, acryloyl group, propioloyl group,methacryloyl group, crotonoyl group, oleoyl group, maleoyl group,fumaroyl group, mesaconoyl group, camphoroyl group, benzoyl group,phthaloyl group, isophthaloyl group, terephthaloyl group, naphthoylgroup, toluoyl group, hydroatropoyl group, atropoyl group, cinnamoylgroup, furoyl group, thenoyl group, nicotinoyl group, isonicotinoylgroup, toluenesulfonyl group, mesyl group and the like.

The above-mentioned cyclic acid-decomposable groups include, forexample, cyclopropyl group, cyclopentel group, cyclohexyl group,cyclohexenyl group, oxocyclohexenyl group, 4-methoxycyclohexyl group,tetrahydropyranyl group, tetrahydrofuranyl group, tetrahydrothiopyranylgroup, tetrahydrothiofuranyl group, 3-bromotetrahydropyranyl group,4-methoxytetrahydropyranyl group, 4-methoxytetrahydrothiopyranyl group,3-tetrahydrothiophene-1,1-dioxide group, 2-1,3-dioxolanyl group,2-1,3-dithioxolanyl group, benzo-2-1,3-dioxolanyl group,benzo-2-1,3-dioxolanyl group and the like.

Among these acid-decomposable groups, preferable are tert-butyl group,benzyl group, tert-butoxycarbonyl group, tert-butoxycarbonylmethylgroup, tertrahydropyranyl group, tetrahydrofuranyl group,tetrahydrothiopyranyl group, tetrahydrothiofuranyl group andtrimethylsilyl group and the like.

The above-mentioned acid-decomposable group-containing resin can beproduced, for example, by introducing at least one acid-decomposablegroup into an alkali-soluble resin or polymerizing or copolymerizing atleast one monomer having at least one acid-decomposable group orpolycondensing or copolycondensing at least one polycondensing componenthaving at least one acid-decomposable group.

Incidentally, the proportion of the acid-decomposable group introducedinto the acid-decomposable group-containing resin (the ratio of thenumber of acid-decomposable groups to the total number of acidicfunctional groups and acid-decomposable groups in the acid-decomposablegroup-containing resin) is preferably 15 to 100%, more preferably 15 to80% and most preferably 15 to 60%.

The Mw of the acid-decomposable group-containing resin is preferably1,000 to 150,000, more preferably 3,000 to 100,000.

These acid-decomposable group-containing resins may be used alone or inadmixture of two or more.

The proportion of the alkali-solubility controller added in thisinvention is preferably 100 parts by weight or less per 100 parts byweight of the polymer (A). When the amount of the alkali-solubilitycontroller is more than 100 parts by weight, the coatability of thecomposition, coating-film strength and the like have a tendency toreduce.

The alkali-solubility controller may be used alone or in admixture oftwo or more in each case of a low molecular weight compound or a highmolecular weight compound (namely, the acid-decomposablegroup-containing resin) and a mixture of the low molecular weightcompound and the high molecular weight compound may also be used.

Acid-Diffusion Controller

The acid-diffusion controller has such an action as to control thediffusion phenomenon in the resist coating-film of the acid generatedfrom the acid generator by irradiation with a radiation and control theundesirable chemical reactions in the unirradiated area. When theacid-diffusion controller is used, the pattern shape, particularly thedegree of formation of a visor in the upper part of the pattern(“T”-shape), the dimension fidelity to mask dimension and the like canbe further improved.

Such acid-diffusion controllers are preferably nitrogen-containingorganic compounds whose basicity is not changed by irradiation with aradiation or heating, and specific examples thereof include ammonia,hexylamine, heptylamine, octylamine, nonylamine, decylamine,dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine,dinonylamine, didecylamine, trimethylamine, triethylamine,tripropylamine, tributylamine, tripentylamine, trihexylamine,triheptylamine, trioctylamine, trinonylamine, tridecylamine, aniline,N-methylaniline, N,N-dimethylaniline, 2-methylaniline, 3-methylaniline,4-methylaniline, 4-nitroaniline, 1-naphthylamine, 2-naphthylamine,diphenylamine, ethylenediamine, tetramethylenediamine,hexamethylenediamine, pyrrolidone, piperidine, imidazole,4-methylimidazole, 4-methyl-2-phenylimidazole, thiabendazole, pyridine,2-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 4-ethylpyridine,1-methyl-4-phenylpyridine, 2-(1-ethylpropyl)pyridine, nicotinamide,dibenzoylthiamine, riboflavin tetrabutyrate, 4,4-diaminodiphenylmethane,4,4′-diaminodiphenyl ether, 4,4,-diaminobenzophenone,4,4,-diaminodiphenylamine, 2,2-bis(4-aminophenyl)propane,2-(3-aminophenyl)-2-(4-aminophenyl)propane,2-(4-aminophenyl)-2-(3-hydroxyphenyl)propane,2-(4-aminophenyl)-2-(4-hydroxyphenyl)propane,1,4-bis[1-(4-aminophenyl)-1-methylethyl]benzene,1,3-bis[1-(4-aminophenyl)-1-methylethyl]benzene, dimethylsuccinate-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidinepolycondensate, poly[{6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl) imino}], bis(1,2,2,6,6-pentamethyl-4-piperidyl)-2-(3,5-di-tert-butyl-4-hydroxybenzyl)-2-butylmalonateand the like.

These acid-diffusion controllers may be used alone or in admixture oftwo or more.

The proportion of the acid-diffusion controller added in this inventionis preferably 0.001 to 10 parts by weight, more preferably 0.005 to 5parts by weight, per 100 parts by weight of the polymer (A). In thiscase, when the amount of the acid-diffusion controller used is less than0.001 part by weight, there is a fear that the pattern shape anddimension fidelity may not be improved under some processing conditions,and when the proportion is more than 10 parts by weight, the sensitivityas a resist and the developability in the exposed portion have atendency to lower.

Various Additives

The radiation sensitive resin composition of this invention may, ifnecessary, contain various additives such as a surfactant, a sensitizerand the like.

The above surfactant has an action to improve the coatability of theradiation sensitive resin composition, striation, developability ofcoating-film of the composition and the like. Such surfactants include,for example, polyoxyethylene lauryl ether, polyoxyethylene stearylether, polyoxyethylene oleyl ether, polyoxyethylene octyl phenyl ether,polyoxyethylene nonyl phenyl ether, polyoxyethylene glycol dilaurate andpolyoxyethylene glycol distearate and also include KP341 (a trade nameof Shin-Ets Chemical Co., Ltd.), Polyflow No. 75, No. 95 (trade names ofKyoeisha Yushi Kagaku Kogyo K. K.), F Top EF301, EF303, EF352 (tradenames of Tokem Products), Megafac F171, F172, F173 (trade names ofDAINIPPON INK & CHEMICALS, INC.), Fluorad FC430, FC431 (trade names ofSumitomo 3M Limited), Asahi Guard AG710, Surflon S-382, SC-101, SC-102,SC-103, SC-104, SC-105, SC-106 (trade names of Asahi Glass Co., Ltd.)and the like.

The amount of the surfactant added is preferably 2 parts by weight orless per 100 parts by weight of the solid content of the radiationsensitive resin composition.

The above-mentioned sensitizer has an action to absorb the energy ofradiation and transfer the energy to the radiation sensitive acidgenerator (B) to thereby increase the amount of acid produced and hasalso an effect that the sensitivity of resist obtained from theradiation sensitive resin composition of this invention is enhanced. Thesensitizer is preferably a ketone, a benzene, an acetophenone, abenzophenone, a naphthalene, a biacetyl, an eocin, rose bengal, apyrene, an anthracene, a phenolthiazine or the like.

The amount of the sensitizer added is preferably 50 parts by weight orless, more preferably 30 parts by weight or less, per 100 parts byweight of the solid content of the radiation sensitive resincomposition.

By compounding a dye or pigment with the composition, the influence ofhalation during irradiation with a radiation can be softened and bycompounding an adhesion promoters with the composition, the adhesionproperties of the coating-film to a substrate can be improved.

Moreover, other additives include halation-preventing agents such as azocompounds, amine compounds and the like, storage stabilizers; defoamingagents; shape-improving agents; and the like.

Solvent

The radiation sensitive resin composition of this invention is dissolvedin a solvent so that the solid concentration becomes, for example, 5 to50% by weight, preferably 20 to 40% by weight when it is used, and thenfiltered through a filter having a pore diameter, for example, about0.2μ to prepare a composition solution.

The solvent to be used in the preparation of the composition solutionincludes, for example, ethylene glycol monoalkyl ethers such as ethyleneglycol monomethyl ether, ethylene glycol monoethyl ether, ethyleneglycol monopropyl ether, ethylene glycol monobutyl ether and the like;ethylene glycol monoalkyl ether acetates such as ethylene glycolmonomethyl ether acetate, ethylene glycol monoethyl ether acetate,ethylene glycol monopropyl ether acetate, ethylene glycol monobutylether acetate and the like; diethylene glycol dialkyl ethers such asdiethylene glycol dimethyl ether, diethylene glycol diethyl ether,diethylene glycol dipropyl ether, diethylene glycol dibutyl ether andthe like; propylene glycol monoalkyl ethers such as propylene glycolmonomethyl ether, propylene glycol monoethyl ether, propylene glycolmonopropyl ether, propylene glycol monobutyl ether and the like;propylene glycol dialkyl ethers such as propylene glycol dimethyl ether,propylene glycol diethyl ether, propylene glycol dipropyl ether,propylene glycol dibutyl ether and the like; propylene glycol monoalkylether acetates such as propylene glycol monomethylether acetate,propylene glycol monoethyl ether acetate, propylene glycol monopropylether acetate, propylene glycol monobutyl ether acetate and the like;lactic acid esters such as methyl lactate, ethyl lactate, n-propyllactate, isopropyl lactate, n-butyl lactate, isobutyl lactate and thelike; aliphatic carboxylic acid esters such as methyl formate, ethylformate, n-propyl formate, isopropyl formate, n-butyl formate, isobutylformate, n-amyl formate, isoamyl formate, methyl acetate, ethyl acetate,n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate,n-amyl acetate, isoamyl acetate, n-hexyl acetate, methyl propionate,ethyl propionate, n-propyl propionate, isopropyl propionate, n-butylpropionate, isobutyl propionate, methyl butyrate, ethyl butyrate,n-propyl butyrate, isopropyl butyrate, n-butyl butyrate, isobutylbutyrate and the like; other esters such as ethyl hydroxyacetate, ethyl2-hydroxy-2-methylpropionate, methyl 3-methoxy-2-methylpropionate(methyl β-methoxybutyrate), methyl, 2-hydroxy-3-methylbutyrate, ethylmethoxyacetate, ethyl ethoxyacetate, methyl 3-methoxypropionate, ethyl3-methoxypropionate, methyl 3-ethoxypropionate, ethyl3-ethoxypropionate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutylacetate, 3-methyl-3-methoxybutyl propionate, 3-methyl-3-methoxybutylbutyrate, methyl acetoacetate, ethyl acetoacetate, methyl pyruvate,ethyl pyruvate and the like; aromatic hydrocarbons such as toluene,xylene and the like; ketones such as methyl ethyl ketone, 2-heptanone,3-heptanone, 4-heptanone, cyclohexanone and the like; amides such asN-methylformamide, N,N-dimethylformamide, N-methylacetamide,N,N-dimethylacetamide, N-methylpyrrolidone and the like; lactones suchas γ-butyrolactone and the like; etc.

These solvents may be used alone or in admixture of two or more.

The amount of the solvent used in the composition solution in thisinvention is preferably 20 to 3,000 parts by weight, more preferably 50to 3,000 parts by weight, and most preferably 100 to 2,000 parts byweight, per 100 parts by weight of the total solid content of thepolymer (A), the radiation sensitive acid generator (B) and theoptionally added dissolution controller and/or additives.

In the formation of a resist pattern from the radiation sensitive resincomposition of this invention, the composition solution is applied to asubstrate such as a silicon wafer, an aluminum-coated wafer or the likeby a means such as a spin coating, a flow coating, a roll coating or thelike to form a resist coating-film, and the resist coating-film isirradiated with a radiation so that the desired pattern is formed. Theradiation used in this case is appropriately selected from ultravioletrays such as i ray and the like; deep ultraviolet rays such as excimerlaser and the like; X rays such as synchrotron radiation or the like;and charged particle beams such as electron beam and the like dependingupon the kind of the radiation sensitive acid generator (B) used. Theirradiation conditions such as irradiation dose and the like areappropriately selected depending upon the compounding recipe of theradiation sensitive resin composition, the kind of the additives and thelike.

In the formation of a resist pattern using the radiation sensitive resincomposition of this invention, it is possible to provide a protectivecoating-film on the resist coating-film for preventing the influence ofbasic impurities or the like contained in the working atmosphere.

In this invention, in order to enhance the apparent sensitivity of theresist coating-film, it is preferable to effect baking after theirradiation (post-exposure baking). The heating conditions for thepost-exposure baking may be varied depending upon the compounding recipeof the radiation sensitive resin composition of this invention, the kindof additives and the like; however, the heating temperature ispreferably 30° to 200° C., more preferably 50° to 150° C.

Subsequently, the irradiated resist coating-film is developed with analkali developer to form the desired resist pattern. The alkalideveloper includes, for example, alkaline compounds such as sodiumhydroxide, potassium hydroxide, sodium carbonate, sodium silicate,sodium metasilicate, ammonia water, ethylamine, n-propylamine,diethylamine, di-n-propylamine, triethylamine, methyldiethylamine,dimethylethanolamine, triethanolamine, tetramethylammonium hydroxide,tetraethylammonium hydroxide, choline, pyrrole, piperidine,1,8-diazabicyclo-[5,4,0]-7-undecene, 1,5-diazabicyclo-[4,3, 0]-5-noneneand the like, and an aqueous alkaline solution having a concentration ofpreferably 1 to 10% by weight, more preferably 2 to 5% by weight is usedas the developer.

To the above developer may be added an aqueous organic solvent such asmethanol, ethanol or the like and a surfactant in appropriate amounts.

Incidentally, when a developer consisting of such an aqueous alkalinesolution is used, the resulting resist pattern is washed with waterafter the development.

The positive radiation sensitive resin composition of this invention canform a highly precise pattern without causing volume shrinkage, peelingfailure and adhesive failure and is excellent in dry etching resistance.

Moreover, the positive radiation sensitive resin composition of thisinvention reacts effectively with various radiations, is excellent inphotolithographic process stability and, in particular, the upper partof the pattern shape formed does not become thinner than the lower partand a rectangular pattern can be formed.

Furthermore, the positive radiation sensitive resin composition of thisinvention is excellent in pattern shape, sensitivity, contrast,developability and the like particularly when deep ultraviolet rays, Xrays or electron beams are used.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention is explained in more detail below referring to Examplesand Comparative Examples; however, this invention should not beconstrued to be limited thereto.

In the Examples, various characteristics were evaluated as follows.

Mw and Mw/Mn

Using a GPC column manufactured by TOSOH CORP. (two G2000H_(XL) columns,one G3000H_(XL) column and one G4000H_(XL) column), the Mw was measuredby a gel permeation chromatograph method in which a monodispersestandard polystyrene was used as a standard under the analysisconditions that the flow rate was 1.0 ml/min, the eluent wastetrahydrofuran, and the column temperature was 40° C.

Optimum Dose of Radiation Irradiated

After irradiation with various radiation doses, like mentioned above,then the development with a 2.38% by weight aqueous tetrahydroammoniumhydroxide solution, water-washing and drying were conducted to form aresist pattern on a silicon wafer with the irradiated-resist coatingfilm. And then the radiation dose necessary for forming a 0.5-μmline-and-space pattern (1L1S) in a 1:1 width was determined as theoptimum radiation dose.

Resolution

The minimum dimension of the resist pattern resolved when a radiationwas irradiated at the optimum radiation dose was determined as theresolution.

Pattern Shape

The lower side dimension La and the upper side dimension Lb of thesquare cross-section of the 1L1S pattern of a line width of 0.5 μmformed on a silicon wafer were measured using a scanning type electronmicroscope. When the resulting pattern satisfied 0.85≦Lb/La≦1 and thepattern had no thinned portion in the vicinity of the substrate and nooverhang at the top (no “T”-shape), said pattern shape was determinedgood. When patterns did not satisfy these conditions, they weredetermined bad.

Process Stability

An irradiation was applied to a resist coating-film formed on a siliconwafer and, immediately thereafter, the resist coating-film was subjectedto post exposure baking and development to obtain a resist pattern.Separately, the resist coating-film irradiated with a radiation wasallowed to stand for two hours after the irradiation and then subjectedto post exposure baking and development to obtain another resistpattern. The shapes of the two resist patterns obtained were compared.

Synthesis Example 1

In 50 g of dioxane were dissolved 20 g of vinylphenol, 20 g oftert-butyl acrylate and 8.5 g of styrene, and then 8.2 g of2,2′-azobisisobutyronitrile was added thereto, after which the resultingsolution was bubbled with a nitrogen gas for 30 minutes. Thereafter, thesolution was heated to 60° C. while the bubbling was continued to effectpolymerization for seven hours. After the polymerization, the solutionwas poured into a large amount of hexane to coagulate the polymer andthe polymer was then recovered. The polymer was dissolved in acetone andthen the resulting solution was poured into hexane again to coagulatethe polymer. This operation was repeated several times to removecompletely the unreacted monomers, after which the polymer was dried at50° C. under vacuum overnight. The polymer thus obtained was white andthe yield was 55%. As a result of ¹H-NMR and ¹³C-NMR analyses, it wasfound that the composition of the polymer was such that vinylphenol,tert-butyl acrylate and styrene were copolymerized at a proportion ofapproximately 2:2:1. Mw was 24,000 and Mw/Mn was 2.8. This polymer isreferred to hereinafter as Polymer (I).

Synthesis Example 2

The same procedure as in Synthesis Example 1 was repeated, except that22 g of isopropenylphenol was substituted for the 20 g of vinyphenol, tosynthesize a polymer. The polymer obtained was white and the yield was45%. As a result of ¹H-NMR and ¹³C-NMR analyses, it was found that thecomposition of the polymer was such that isopropenylphenol, tert-butylacrylate and styrene were copolymerized at a ratio of approximately2:3:1. Mw was 28,000 and Mw/Mn was 2.6. This polymer is referred tohereinafter as Polymer (II).

Synthesis Example 3

The same procedure as in Synthesis Example 1 was repeated, except that15 g of tert-butyl methacrylate was substituted for the 20 g oftert-butyl acrylate and 3 g of methyl methacrylate was substituted forthe 8.5 g of styrene, to synthesize a polymer. The polymer obtained waswhite and the yield was 60%. As a result of ¹H-NMR and ¹³C-NMR analyses,it was found that the composition of the polymer was such thatvinylphenol, tert-butyl methacrylate and methyl methacrylate werecopolymerized at a ratio of approximately 5:3:1. Mw was 22,000 and Mw/Mnwas 2.7. This polymer is referred to hereinafter as Polymer (III).

Synthesis Example 4

The same procedure as in Synthesis Example 3 was repeated, except that1.2 g of acrylonitrile was substituted for the 3 g of methylmethacrylate, to synthesize a polymer. The polymer thus obtained wasyellowish white and the yield was 55%. As a result of ¹H-NMR and ¹³C-NMRanalyses, it was found that the composition of the polymer was such thatvinylphenol, tert-butyl methacrylate and acrylonitrile werecopolymerized at a ratio of approximately 5:3:1. Mw was 29,000 and Mw/Mnwas 2.4. This polymer is referred to hereinafter as Polymer (V).

Synthesis Example 5

In 59 g of propylene glycol monomethyl ether were dissolved 22 g ofisopropenylphenol, 11 g of tert-butyl acrylate, 2 g of α-methylstyreneand 1 g of methyl vinyl ketone, and then, 2.5 g of benzoyl peroxide wasadded to the resulting solution, after which the solution was bubbledwith a nitrogen gas for 30 minutes. Thereafter, the solution was heatedto 80° C. while the bubbling was continued to effect polymerization for48 hours. After the polymerization, the solution was poured into a largeamount of hexane to coagulate a polymer. This polymer was dissolved inacetone and then coagulated in hexane again. This operation was repeatedseveral times to remove the unreacted monomers completely and thepolymer was dried at 50° C. under vacuum overnight. The polymer thusobtained was white and the yield was 55%. As a result of ¹H-NMR and¹³C-NMR analyses, it was found that the composition of the polymer wassuch that isopropenylphenol, tert-butyl acrylate, α-methylstyrene andmethyl vinyl ketone were copolymerized at a ratio of approximately13:7:2:1. Mw was 18,000 and Mw/Mn was 3.2. This polymer is referred tohereinafter as Polymer (V).

Synthesis Example 6

The same procedure as in Synthesis Example 5 was repeated, except that10 g of vinylphenol, 12 g of isopropenylphenol, 10 g of tert-butylmethacrylate and 3 g of styrene were dissolved in 50 g of toluene, toproduce a polymer. The polymer thus obtained was white and the yield was55%. As a result of ¹H-NMR and ¹³C-NMR analyses, it was found that thecomposition of the polymer was such that vinylphenol, isopropenylphenol,tert-butyl methacrylate and styrene were copolymerized at a ratio ofapproximately 4:3:3:1. Mw was 31,000 and Mw/Mn was 2.5. This polymer isreferred to hereinafter as Polymer (VI).

Comparative Synthesis Example 1

In 50 ml of dioxane were dissolved 12 g of polyhydroxystyrene and 5 g oftriethylamine. To this mixed solution was added 4 g of di-tert-butylcarbonate while the solution was stirred, and then stirred at roomtemperature for 6 hours, after which oxalic acid was added to thesolution to neutralize the triethylamine. This solution was poured intoa large amount of water to coagulate a polymer and the polymer waswashed with pure water several times to obtain a white polymer. Theyield was 85%. As a result of ¹H-NMR and ¹³C-NMR analyses, it was foundthat the composition of the polymer was such that vinylphenol, andtert-butoxycarbonyloxyvinylphenol were copolymerized at a ratio ofapproximately 7:3. Mw was 9,200 and Mw/Mn was 2.8. This polymer isreferred to hereinafter as Polymer (VII).

Comparative Synthesis Example 2

The same procedure as in Synthesis Example 1 was repeated, except that24 g of vinylphenol and 19 g of tert-butyl methacrylate were dissolvedin 50 g of dioxane, to produce a polymer. The polymer obtained was whiteand the yield was 65%. As a result of ¹H-NMR and ¹³C-NMR analyses, itwas found that the composition of the polymer was such that vinylphenoland tert-butyl methacrylate were copolymerized at a ratio ofapproximately 7:3. Mw was 23,000 and Mw/Mn was 2.3. This polymer isreferred to hereinafter as Polymer (VIII).

Examples 1 to 16 and Comparative Examples 1 and 2

The polymer (A), the radiation sensitive acid generator (B) andoptionally the dissolution controller, the acid-diffusion controller andthe solvent shown in Table 1 were mixed in the proportion shown in Table1 to form a uniform solution, and thereafter, the solution was filteredthrough a membrane filter having a pore diameter of 0.2 μm to prepare aresist solution.

The resist solution was coated on a silicon wafer by a spin coater andthen prebaked at 90° C. for 100 seconds to form a resist coating-filmhaving a film thickness of 1.0 μm, after which the resist coating-filmwas irradiated with the various radiations shown in Table 2 andthereafter subjected to post exposure baking at 90° C. for 120 seconds.Subsequently, the irradiated and baked resist coating-film was developedwith 2.38% by weight aqueous tetramethylammonium hydroxide solution by adipping method at 23° C. for 60 seconds, and then washed with water for30 seconds. The results obtained are shown in Table 2.

TABLE 1 Alkali- Acid- Acid solubility diffusion Polymer generatorcontroller controller Solvent Part Part Part Part Part Kind by wt. Kindby wt. Kind by wt. Kind by wt. Kind by wt. Example 1 I 100 P1 3 — — — —EL 350 2 I  70 P2 3 D1 30 — — EL/EEP 200/100 3 II 100 P3 5 — — — — EL/BA200/100 4 III 100 P1 3 — — — — PGMEA 300 5 IV 100 P2 3 — — — — MAX 300 6V 100 P4 10  — — — — MMP 300 7 VI  80 P1 3 D2 20 — — EL/MMP 150/150 8 I100 P5 5 — — — — EL 350 9 II  70 P6 3 D1 30 — — EL/EEP 200/100 10  II100 P1/P5 3/2 — — — — PGMEA 300 11  III 100 P7 3 — — — — EL/BA 200/10012  V 100 P5/P7 2/2 — — — — MMP 300 13  I 100 P1 3 — — C1 1.2 EL 350 14 II 100 P3 5 — — C3 2.0 EL/BA 200/100 15  I 100 P5 5 — — C4 2.0 EL 35016  II 100 P1/P5 3/2 — — C2 1.2 PGMEA 300 Comp. Ex. 1 VII 100 P1 3 — — —— ECA 300 2 VIII 100 P2 3 — — — — PGMEA 300

TABLE 2 Optimum dose Pattern Process Radiation source of radiationResolution shape stability Example 1 KrF excimer laser (248 nm) 30mJ/cm² 0.25 μm Good Good 2 KrF excimer laser (248 nm) 35 mJ/cm² 0.25 μmGood Good 3 KrF excimer laser (248 nm) 45 mJ/cm² 0.25 μm Good Good 4 KrFexcimer laser (248 nm) 30 mJ/cm² 0.25 μm Good Good 5 Electron beam 3μC/cm² 0.25 μm Good Good (beam dia. 0.25 μm) 6 i ray (365 nm) 180 msec0.35 μm Good Good 7 X ray (palladium Lα) 100 mJ/cm² 0.30 μm Good Good μ= 0.347 nm 8 Electron beam 3 μC/cm² 0.25 μm Good Good (beam dia. 0.25μm) 9 KrF excimer laser (248 nm) 45 mJ/cm² 0.25 μm Good Good 10  KrFexcimer laser (248 nm) 30 mJ/cm² 0.25 μm Good Good 11  KrF excimer laser(248 nm) 40 mJ/cm² 0.25 μm Good Good 12  KrF excimer laser (248 nm) 35mJ/cm² 0.25 μm Good Good 13  KrF excimer laser (248 nm) 35 mJ/cm² 0.23μm Good Good 14  KrF excimer laser (248 nm) 50 mJ/cm² 0.23 μm Good Good15  KrF excimer laser (248 nm) 40 mJ/cm² 0.23 μm Good Good 16  KrFexcimer laser (248 nm) 35 mJ/cm² 0.23 μm Good Good Comp. Example 1 KrFexcimer laser (248 nm) 20 mJ/cm² 0.45 μm Bad Bad Overhang No patternformed 2 KrF excimer laser (248 nm) 15 mJ/cm² 0.30 μm Bad Bad Upper partUpper part of pattern of pattern was thinned. was thinned.

In Tables 1 and 2, the symbols used for the acid generator and solventhave the following meanings:

Radiation sensitive acid generator

P1: Triphenylsulfonium triflate

P2: Diphenyliodonium hexafluoroantimonate

P3: Pyrogallolmethanesulfonic acid triester

P4: Compound represented by the following structural formula (3):

 wherein D represents the substituent shown by the formula (4) or ahydrogen atom;

 and 85% on average of D is the substituent shown by the formula (4) and15% on average of D is a hydrogen atom.

P5:N-(Trifluoromethylsulfonyloxy)-bicyclo-[2,2,1]-hept-5-ene-2,3-dicarboximide

P6: N-(Camphanylsulfonyloxy)naphthylimide

P7: N-(2-Trifluoromethylphenylsulfonyloxy)phthalimide

Alkali-solubility controller

D1: Compound represented by the structural formula (d1):

D2: Compound represented by the structural formula (d2):

Acid-diffusion controller

C1: Tripropylamine

C2: Tri-n-butylamine

C3: Diaminodiphenylmethane

C4: Octylamine

Solvent

EL: Ethyl lactate

EEP: Ethyl 3-ethoxypropionate

MMP: Methyl 3-methoxypropionate

PGMEA: Propylene glycol monomethyl ether acetate

BA: Butyl acetate

MAK: Methyl amyl ketone

ECA: Ethyl Cellosolve acetate

What is claimed is:
 1. A radiation sensitive resin composition whichconsists essentially of (A) a polymer which becomes alkali-soluble inthe presence of an acid and (B) a radiation sensitive acid generatorwhich generates an acid upon irradiation with a radiation, said polymer(A) comprising two recurring units A and B represented by the generalformulas (1) and (2), respectively, and a recurring unit C which acts toreduce the solubility of the polymer in an alkali developer after theirradiation:

wherein R¹ represents a hydrogen atom or a methyl group and R²represents a hydrogen atom or a methyl group, and wherein the recurringunit C is derived from at least one organic compound which is free fromany acidic substituent and selected from the group consisting ofstyrene, α-methylstyrene, p-methylstyrene, methyl (meth) acrylate, ethyl(meth) acrylate, propyl (meth) acrylate, (meth) acrylamide and (meth)arylonitrile.
 2. The radiation sensitive resin composition according toclaim 1, wherein the recurring unit represented by the general formula(1) corresponds to at least one monomer selected from the groupconsisting of vinylphenol and α-isopropenylphenol.
 3. The radiationsensitive resin composition according to claim 1, wherein the recurringunit represented by the general formula (2) corresponds to at least onemonomer selected from the group consisting of tert-butyl acrylate andtert-butyl methacrylate.
 4. The radiation sensitive resin compositionaccording to claim 1, wherein the polystyrene-reduced weight-averagemolecular-weight (Mw) of the polymer (A) is 1,500 to 300,000.
 5. Theradiation sensitive resin composition according to claim 1, wherein thepolystyrene-reduced weight-average molecular-weight of the polymer (A)is 3,000 to 300,000.
 6. The radiation sensitive resin compositionaccording to claim 1, wherein the ratio of the polystyrene-reducedweight-average molecular-weight (Mw) of the polymer (A) to thepolystyrene-reduced number-average molecular-weight (Mn) of the polymer(A) (Mw/Mn) is 1 to
 5. 7. The radiation sensitive resin compositionaccording to claim 6, wherein the ratio (Mw/Mn) is 1.5 to 3.5.
 8. Theradiation sensitive resin composition according to claim 1, wherein theproportion of the number of the recurring units represented by thegeneral formula (1) in the polymer (A) is 5 to 75% of the total numberof all the recurring units contained in the polymer (A).
 9. Theradiation sensitive resin composition according to claim 1, wherein theproportion of the number of the recurring units represented by thegeneral formula (2) in the polymer (A) is 10 to 70% of the total numberof all the recurring units contained in the polymer (A).
 10. Theradiation sensitive resin composition according to claim 1, wherein theproportion of the number of the recurring units which act to reduce thesolubility of the polymer (A) in the alkali developer in the polymer (A)is 0.5 to 50% of the total number of all the recurring units containedin the polymer (A).
 11. The radiation sensitive resin compositionaccording to claim 1, wherein the radiation sensitive acid generator (B)is at least one compound selected from the group consisting of oniumsalts, halogen-containing compounds, sulfone compounds, sulfonatecompounds and quinonediazide compounds.
 12. The radiation sensitiveresin composition according to claim 1, wherein the amount of theradiation sensitive acid generator (B) used is 0.05 to 20 parts byweight per 100 parts by weight of the polymer (A).
 13. The radiationsensitive resin composition according to claim 1, wherein the amount ofthe radiation sensitive acid generator (B) used is 0.1 to 15 parts byweight per 100 parts by weight of the polymer (A).
 14. The radiationsensitive resin composition according to claim 1, which further containsan alkali-solubility controller.
 15. The radiation sensitive resincomposition according to claim 14, wherein the alkali-solubilitycontroller is a compound having an acidic functional group which hasbeen substituted by an acid-decomposable group.
 16. The radiationsensitive resin composition according to claim 1, which further containsan acid-diffusion controller.
 17. The radiation sensitive resincomposition according to claim 16, wherein the acid-diffusion controlleris a nitrogen-containing compound whose basicity is not changed byirradiation or heating.
 18. A radiation sensitive resin compositionwhich consists essentially of (A) a polymer which becomes alkali-solublein the presence of an acid and (B) a radiation sensitive acid generatorwhich generates an acid upon irradiation with a radiation, said polymer(A) comprising two recurring units A and B represented by the generalformulas (1) and (2) and a recurring unit C which acts to reduce thesolubility of the polymer in an alkali developer after the irradiation:

wherein R¹ represents a hydrogen atom or a methyl group and R²represents a hydrogen atom or a methyl group, and wherein the recurringunit C is derived from at least one organic compound which is free fromany acidic substituent and selected from the group consisting of heteroatom-containing aromatic vinyl compounds, vinyl ketone compounds andhetero atom-containing alicyclic ring compounds.
 19. The radiationsensitive resin composition according to claim 11, wherein the oniumsalt is at least one compound selected from the group consisting ofdiphenyliodonium triflate, diphenyliodonium pyrenesulfonate,diphenyliodonium dodecylbenzenesulfonate, triphenylsulfonium triflate,triphenylsulfonium hexafluoroantimonate, diphenyliodoniumhexafluoroantimonate, triphenylsulfonium naphthalenesulfonate,(hydroxyphenyl) benzylmethylsulfonium toluenesulfonate.
 20. Theradiation sensitive resin composition according to claim 1, wherein theratio of the polystyrene-reduced weight-average molecular weight (Mw) ofthe polymer (A) to the polystyrene-reduced number average molecularweight (Mn) of the polymer (A) is 1 to
 5. 21. The radiation sensitiveresin composition according to claim 1, which further contains analkali-solubility controller.
 22. The radiation sensitive resincomposition according to claim 1, which further contains anacid-diffusion controller.
 23. The radiation sensitive resin compositionaccording to claim 18, which further contains an alkali-solubilitycontroller.
 24. The radiation sensitive resin composition according toclaim 18, which further contains an acid-diffusion controller.
 25. Aradiation sensitive resin composition which comprises (A) a polymerwhich becomes alkali-soluble in the presence of an acid and (B) aradiation sensitive acid generator which generates an acid uponirradiation with a radiation, said polymer (A) comprising two recurringunits A and B represented by the general formulas ( 1 ) and ( 2 ),respectively, and a recurring unit C which acts to reduce the solubilityof the polymer in an alkali developer after the irradiation:

wherein R ¹ represents a hydrogen atom or a methyl group and R ²represents a hydrogen atom or a methyl group, and wherein the recurringunit C is derived from at least one organic compound which is free fromany acidic substituent and selected from the group consisting ofstyrene, alpha-methylstyrene, p-methylstyrene, methyl (meth) acrylate,ethyl (meth) acrylate, propyl (meth) acrylate, (meth) acrylamide and(meth) arylonitrile.
 26. The radiation sensitive resin compositionaccording to claim 25, wherein the recurring unit represented by thegeneral formula ( 1 ) corresponds to at least one monomer selected fromthe group consisting of vinylphenol and alpha-isopropenylphenol.
 27. Theradiation sensitive resin composition according to claim 25, wherein therecurring unit represented by the general formula ( 2 ) corresponds toat least one monomer selected from the group consisting of tert-butylacrylate and tert-butyl methacrylate.
 28. The radiation sensitive resincomposition according to claim 25, wherein the polystyrene-reducedweight-average molecular-weight (Mw) of the polymer (A) is 1,500 to300,000.
 29. The radiation sensitive resin composition according toclaim 25, wherein the polystyrene-reduced weight-averagemolecular-weight of the polymer (A) is 3,000 to 300,000.
 30. Theradiation sensitive resin composition according to claim 25, wherein theratio of the polystyrene-reduced weight-average molecular-weight (Mw) ofthe polymer (A) to the polystyrene-reduced number-averagemolecular-weight (Mn) of the polymer (A) (Mw/Mn) is 1 to
 5. 31. Theradiation sensitive resin composition according to claim 30, wherein theratio (Mw/Mn) is 1.5 to 3.5.
 32. The radiation sensitive resincomposition according to claim 25, wherein the proportion of the numberof the recurring units represented by the general formula ( 1 ) in thepolymer (A) is 5 to 75 % of the total number of all the recurring unitscontained in the polymer (A).
 33. The radiation sensitive resincomposition according to claim 25, wherein the proportion of the numberof the recurring units represented by the general formula ( 2 ) in thepolymer (A) is 10 to 70 % of the total number of all the recurring unitscontained in the polymer (A).
 34. The radiation sensitive resincomposition according to claim 25, wherein the proportion of the numberof the recurring units which act to reduce the solubility of the polymer(A) in the alkali developer in the polymer (A) is 0.5 to 50 % of thetotal number of all the recurring units contained in the polymer (A).35. The radiation sensitive resin composition according to claim 25,wherein the radiation sensitive acid generator (B) is at least onecompound selected from the group consisting of onium salts,halogen-containing compounds, sulfone compounds, sulfonate compounds andquinonediazide compounds.
 36. The radiation sensitive resin compositionaccording to claim 25, wherein the amount of the radiation sensitiveacid generator (B) used is 0.05 to 20 parts by weight per 100 parts byweight of the polymer (A).
 37. The radiation sensitive resin compositionaccording to claim 25, wherein the amount of the radiation sensitiveacid generator (B) used is 0.1 to 15 parts by weight per 100 parts byweight of the polymer (A).
 38. The radiation sensitive resin compositionaccording to claim 25, which further contains an alkali-solubilitycontroller.
 39. The radiation sensitive resin composition according toclaim 38, wherein the alkali-solubility controller is a compound havingan acidic functional group which has been substituted by anacid-decomposable group.
 40. The radiation sensitive resin compositionaccording to claim 25, which further contains an acid-diffusioncontroller.
 41. The radiation sensitive resin composition according toclaim 40, wherein the acid-diffusion controller is a nitrogen-containingcompound whose basicity is not changed by irradiation or heating.
 42. Aradiation sensitive resin composition which comprises (A) a polymerwhich becomes alkali-soluble in the presence of an acid and (B) aradiation sensitive acid generator which generates an acid uponirradiation with a radiation, said polymer (A) comprising two recurringunits A and B represented by the general formulas ( 1 ) and ( 2 ) and arecurring unit C which acts to reduce the solubility of the polymer inan alkali developer after the irradiation:

wherein R ¹ represents a hydrogen atom or a methyl group and R ²represents a hydrogen atom or a methyl group, and wherein the recurringunit C is derived from at least one organic compound which is free fromany acidic substituent and selected from the group consisting of heteroatom-containing aromatic vinyl compounds, vinyl ketone compounds andhetero atom-containing alicyclic ring compounds.
 43. The radiationsensitive resin composition according to claim 35, wherein the oniumsalt is at least one compound selected from the group consisting ofdiphenyliodonium triflate, diphenyliodonium pyrenesulfonate,diphenyliodonium dodecylbenzenesulfonate, triphenylsulfonium triflate,triphenylsulfonium hexafluoroantimonate, diphenyliodoniumhexafluoroantimonate, triphenylsulfonium naphthalenesulfonate,(hydroxyphenyl)benzylmethylsulfonium toluenesulfonate.
 44. The radiationsensitive resin composition according to claim 25, wherein the ratio ofthe polystyrene-reduced weight-average molecular weight (Mw) of thepolymer (A) to the polystyrene-reduced number average molecular weight(Mn) of the polymer (A) is 1 to
 5. 45. The radiation sensitive resincomposition according to claim 25, which further contains analkali-solubility controller.
 46. The radiation sensitive resincomposition according to claim 25, which further contains anacid-diffusion controller.
 47. The radiation sensitive resin compositionaccording to claim 42, which further contains an alkali-solubilitycontroller.
 48. The radiation sensitive resin composition according toclaim 42, which further contains an acid-diffusion controller.
 49. Thecomposition of claim 1, wherein said composition further consistsessentially of a solvent.
 50. The composition of claim 49, wherein saidcomposition further consists essentially of a surfactant.
 51. Thecomposition of claim 49, wherein said composition further consistsessentially of a sensitizer.
 52. The composition of claim 51, whereinsaid sensitizer is added in amount of no more than fifty parts byweight, per one hundred parts by weight of solid content of saidradiation sensitive resin composition.
 53. The composition of claim 50,wherein said surfactant is present in amounts of no more than two partsby weight per one hundred parts by weight of solid content of saidradiation sensitive resin composition.
 54. The composition of claim 49,wherein said composition further consists essentially of a dye orpigment.
 55. The composition of claim 49, wherein said compositionfurther consists essentially of an adhesion promoter.
 56. Thecomposition of claim 49, wherein said composition further consistsessentially of at least one additive selected from the group consistingof a halation-preventing agent, a storage stabilizer, a defoaming agentand a shape-improving agent.
 57. The composition of claim 49, whereinsaid solvent comprises ethyl lactate.